The present invention relates to a force detector using capacitance elements or variable resistance elements and, more specifically, to a force detector suitable for being applied to an input device which obtains operational inputs indicating predetermined operation amounts into an electronic apparatus such as a portable telephone, game machine, or the like which executes predetermined processing based on predetermined programs.
In an electronic apparatus such as a portable telephone, game machine, or the like, a predetermined operational input by a user is accepted, and based on this operational input, an execution of program proceeds. Normally, such an operational input is accepted while a user looks at a cursor or other objects displayed on a display screen, and an input indicating one of four directions including upward, downward, rightward, and leftward directions, or one of eight directions including diagonal directions as well are generally required. A device called a joystick has been used for executing such an input with directivity. Such type of device normally includes a built-in two-dimensional force detector which detects a direction and an operation amount of the applied operational input by independently detecting a component in the X-axis direction and a component in the Y-axis direction. For example, an operational input with a +5 component in the X-axis direction indicates an operation amount of 5 in the rightward direction, and an operational input with a xe2x88x928 component in the Y-axis direction indicates an operation amount of 8 in the downward direction. Of course, detection of an operational input applied diagonally is also possible by carrying out an operation for composing the component in the X-axis direction and the component in the Y-axis direction, and so forth.
In an electronic apparatus such as a portable telephone, game machine, or the like, a clicking input is required as well as the abovementioned operational input with directivity. This clicking input is basically an input indicating a binary condition of ON/OFF, and it is important to provide an operator with a clicking sensation through this input. Therefore, a reaction force must be applied with respect to a pressing force applied from the operator""s finger while securing some degree of stroke. As a switch suitable for such ON/OFF inputs with a clicking sensation, switches using elasticity of elastic materials such as rubber and metals have been generally used, and force detectors with a function for making operational inputs in predetermined directions as well as clicking inputs have been made practicable.
As relatively inexpensive input devices for electronic apparatuses, force detectors using capacitance elements have been frequently used. For a force detector using a capacitance element, a structure in which the distance between a couple of electrodes is changed by externally applied forces is employed, and by electrically detecting this electrode distance as a capacitance value for the capacitance element, the externally applied forces can be determined. Thus, basic components of a force detector using a capacitance element are a pair of electrodes, wherein advantages of a simple structure and low parts costs can be obtained. Therefore, a force detector using a capacitance element has been widely used as an input device for an electronic apparatus such as a portable telephone, game machine, or the like.
As a method for electrically detecting a capacitance value C of a capacitance element, a method using a C/V converter circuit for converting the capacitance value C into a voltage value V and a method using a C/f converter circuit for converting a capacitance value C into a frequency f have been generally known. However, general C/V converter circuits and C/f converter circuits have oscillation circuits inside, so that power consumption during operation is relatively great. Therefore, if conventional force detectors using such capacitance elements are installed into various electronic apparatuses, power consumption increases as a whole. Particularly, a design in which battery consumption is reduced as long as possible has been demanded for electronic apparatuses such as a portable telephone, game machine, or the like which are operated by built-in batteries. Therefore, a force detector using a capacitance element is disadvantageous in terms of power consumption although it is advantageous in terms of manufacturing costs.
Of course, a measure for reducing the entire power consumption by intermittently operating a C/V converter circuit or C/f converter circuit with great power consumption can be taken. For example, if an intermittent operation with 200 msec periods is carried out in which the circuit is operated for 20 msec and then stopped for the next 180 msec, five measurements per second are possible while the power consumption is reduced to be one tenth. However, even by taking this measure, wasteful power consumption cannot be completely suppressed. Considering the actual use pattern of a portable telephone or the like, the period of input operation for cursor movements or the like is very short, so that operation of circuits with great power consumption while an operator does not carry out operational inputs at all is not efficient.
Also, in Japanese Patent Application No. 2000-132012, a force detector using a variable resistance element is proposed. In this detector, a variable resistance element whose resistance value changes in accordance with applied pressures is used, and externally applied forces can be detected by detecting changes in resistance value of this variable resistance element.
In this force detector using the variable resistance element, to obtain a detection value of an applied force, a measurement of electric resistance of a resistor is essential. However, to measure the electric resistance of the resistor, it is necessary to make a current flow in the resistor, and some degree of power consumption is inevitable during the measurement. Therefore, if the abovementioned force detector using the variable resistance element is installed into various electronic apparatuses, power consumption increases as a whole.
The object of the invention is, therefore, to provide a force detector using capacitance elements or variable resistance elements wherein power consumption can be efficiently suppressed.
(1) The first feature of the present invention resides in a force detector having a function for detecting a strength of an applied external force, comprising:
a substrate;
an elastic deformable body which is disposed at a position opposed to the substrate, at least a portion of the elastic deformable body being made of material having elastic deformability, and the elastic deformable body displacing with respect to the substrate due to an elastic deformation caused by the applied external force;
a force detecting element disposed between the substrate and the elastic deformable body and changes in a predetermined electrical characteristic due to a displacement of the elastic deformable body;
a switching element including a pair of contacting electrodes and carrying out a switching function so that an electrical insulated condition is normally maintained between the pair of contacting electrodes, and when an external force with more than a predetermined strength is applied to the elastic deformable body, an electrical conductive condition is obtained between the pair of contacting electrodes in response to a deformation of the elastic deformable body; and
a detection circuit for detecting a change in the electrical characteristic of the force detecting element as an electric signal;
wherein the detection circuit selectively operates in two modes of a detection mode and a standby mode, the detection circuit performing a detecting function for outputting a change in the electrical characteristic as an electric signal when the detection circuit operates in the detection mode, the detection circuit maintaining a standby condition waiting for a transition to the detection mode without performing the detecting function when the detection circuit operates in the standby mode, a power consumption in the standby mode being less than a power consumption in the detection mode; and
wherein the standby mode is selected when an electrical condition between the pair of contacting electrodes is an insulated condition, and the detection mode is selected when an electrical condition between the pair of contacting electrodes is a conductive condition.
(2) The second feature of the present invention resides in a force detector having the first feature:
wherein the pair of contacting electrodes included in the switching element are comprised of a contacting fixed electrode disposed on the substrate and a contacting displacing electrode disposed on the elastic deformable body, and when an external force with more than the predetermined strength is applied to the elastic deformable body, due to a deformation of the elastic deformable body, the contacting displacing electrode comes into physical contact with the contacting fixed electrode.
(3) The third feature of the present invention resides in a force detector having the first feature:
wherein the switching element includes a pair of contacting electrodes disposed on the substrate and a mediating electrode which simultaneously comes into contact with both of the pair of contacting electrodes to make an electrical conductive condition between the pair of contacting electrodes, and
the mediating electrode is disposed so that the mediating electrode is normally maintained to be contacted with neither of the pair of contacting electrodes, or contacted with either one of the pair of contacting electrodes, and when an external force with more than the predetermined strength is applied to the elastic deformable body, due to a deformation of the elastic deformable body, the mediating electrode simultaneously comes into contact with both of the pair of contacting electrodes.
(4) The fourth feature of the present invention resides in a force detector having the third feature:
wherein the mediating electrode is formed at a position at which a deformation of the elastic deformable body occurs.
(5) The fifth feature of the present invention resides in a force detector having the fourth feature:
wherein the pair of contacting electrodes are comprised of a first ring-shaped electrode and a second ring-shaped electrode disposed adjacent to and outside the first electrode, and
the mediating electrode is disposed at a position so as to be able to be simultaneously contacted with both the first ring-shaped electrode and the second ring-shaped electrode at any position.
(6) The sixth feature of the present invention resides in a force detector having the fourth feature:
wherein the pair of contacting electrodes are comprised of a plural number N of electrodes belonging to a first group and a plural number N of electrodes belonging to a second group which are arranged on the substrate so that the i-th electrode (1xe2x89xa6ixe2x89xa6N) belonging to the first group and the i-th electrode belonging to the second group are adjacent to each other, a pair of contacting electrodes are formed of an electrode belonging to the first group and an electrode belonging to the second group which are adjacent to each other, and a total of N pairs of contacting electrodes are provided.
(7) The seventh feature of the present invention resides in a force detector having the sixth feature:
wherein electrodes belonging to the first group and electrodes belonging to the second group are alternately disposed along a circumference defined on the substrate, and
the mediating electrode is disposed along a circumference on the elastic deformable body opposed to the circumference defined on the substrate.
(8) The eighth feature of the present invention resides in a force detector having the third feature:
wherein a domed structure is provided and disposed turned down in a vicinity of the pair of contacting electrodes on the substrate, the domed structure having a property whereby a vicinity of an apex elastically deforms to be convexed downward when a downward pressing force with more than predetermined strength is applied to a vicinity of the apex, and having a conductive contacting surface which is used as a mediating electrode so that, when an external force with more than the predetermined strength is applied to the elastic deformable body, a shape of the domed structure is inverted due to a deformation of the elastic deformable body, and the conductive contacting surface simultaneously comes into contact with both of the pair of contacting electrodes.
(9) The ninth feature of the present invention resides in a force detector having the eighth feature:
wherein the mediating electrode is comprised of a conductive contacting surface which extends from a lower surface part of an apex of the domed structure to a bottom circumferential part of the domed structure, a first electrode among the pair of contacting electrodes being disposed at a position to be contacted with the bottom circumferential part of the domed structure, a second electrode among the pair of contacting electrodes being disposed at a center of the domed structure, and
the mediating electrode normally maintains a contacted condition with only the first electrode, and simultaneously comes into contact with both of the first electrode and the second electrode due to a shape inversion of the domed structure when an external force with more than the predetermined strength is applied to the elastic deformable body.
(10) The tenth feature of the present invention resides in a force detector having the eighth feature:
wherein the pair of contacting electrodes are disposed in a region surrounded by a bottom circumferential surface of the domed structure, the mediating electrode comprised of a conductive contacting surface formed on a lower surface of an apex of the domed structure normally maintains non-contact condition to be contacted with neither of the pair of contacting electrodes, and when an external force with more than the predetermined strength is applied to the elastic deformable body, the mediating electrode simultaneously comes into contact with both of the pair of contacting electrodes due to a deformation of the elastic deformable body.
(11) The eleventh feature of the present invention resides in a force detector having one of the first to the tenth features:
wherein a capacitance element is used as a force detecting element, and the detection circuit detects a capacitance value of the capacitance element as an electric signal, the capacitance element comprising a detecting fixed electrode provided on the substrate and a detecting displacing electrode provided at a position on the elastic deformable body which is opposed to the detecting fixed electrode and at which a displacement occurs.
(12) The twelfth feature of the present invention resides in a force detector having the third feature:
wherein a capacitance element is used as a force detecting element, and the detection circuit detects a capacitance value of the capacitance element as an electric signal, the capacitance element comprising a detecting fixed electrode provided on the substrate and a detecting displacing electrode provided at a position on the elastic deformable body which is opposed to the detecting fixed electrode and at which a displacement occurs, the mediating electrode and the detecting displacing electrode being electrically connected, and the detection circuit has a function for detecting a capacitance value between a contacting electrode which is contacted with the mediating electrode and the detecting fixed electrode as a capacitance value of the capacitance element in the detection mode.
(13) The thirteenth feature of the present invention resides in a force detector having the third feature:
wherein a capacitance element is used as a force detecting element, and the detection circuit detects a capacitance value of the capacitance element as an electric signal, the capacitance element comprising a detecting fixed electrode provided on the substrate and a detecting displacing electrode provided at a position on the elastic deformable body which is opposed to the detecting fixed electrode and at which a displacement occurs,
a domed structure is provided and disposed turned down in a vicinity of the pair of contacting electrodes on the substrate, the domed structure having a property whereby a vicinity of an apex elastically deforms to be convexed downward when a downward pressing force with more than predetermined strength is applied to a vicinity of the apex, and having a conductive contacting surface which is used as a mediating electrode so that, when an external force with more than the predetermined strength is applied to the elastic deformable body, a shape of the domed structure is inverted due to a deformation of the elastic deformable body, and the conductive contacting surface simultaneously comes into contact with both of the pair of contacting electrodes, and
at least an upper surface and a lower surface of a vicinity part of an apex of the domed structure are comprised of a conductive material and are electrically connected with each other, a mediating conductive layer electrically connected to the detecting displacing electrode is formed at a portion of the elastic deformable body to be contacted with a vicinity part of the apex of the domed structure, and the detection circuit has a function for detecting a capacitance value between one of the pair of contacting electrodes which is electrically contacted with the mediating conductive layer via the domed structure and the detecting fixed electrode as a capacitance value of the capacitance element in the detection mode.
(14) The fourteenth feature of the present invention resides in a force detector having one of the eleventh to the thirteenth features:
wherein on a surface of at least either one of the detecting fixed electrode and the detecting displacing electrode, an insulating film is formed to prevent an electrical contact between the detecting fixed electrode and the detecting displacing electrode.
(15) The fifteenth feature of the present invention resides in a force detector having one of the eleventh to the fourteenth features:
wherein the detection circuit has a C/V converter circuit for converting a capacitance value C of the capacitance element into a voltage value V, and a control is carried out so that the C/V converter circuit is operated in the detection mode and is not operated in the standby mode.
(16) The sixteenth feature of the present invention resides in a force detector having the fifteenth feature:
wherein the C/V converter circuit comprises an oscillation circuit for supplying an AC signal to one of the electrodes comprising the capacitance element, and a switching circuit which causes the oscillation circuit to oscillate in the detection mode, and stop an oscillation of the oscillation circuit in the standby mode.
(17) The seventeenth feature of the present invention resides in a force detector having one of the eleventh to the fourteenth features:
wherein the detection circuit has a C/f converter circuit for converting a capacitance value C of the capacitance element into a frequency f, and control is carried out so that the C/f converter circuit is operated in the detection mode and is not operated in the standby mode.
(18) The eighteenth feature of the present invention resides in a force detector having one of the eleventh to the seventeenth features:
wherein the detecting displacing electrode is comprised of a conductive coating layer applied on a surface of an integrally molded rubber.
(19) The nineteenth feature of the present invention resides in a force detector having one of the first to the tenth features:
wherein a variable resistance element with a property by which a resistance value between two predetermined points changes depending on an applied pressure is used as a force detecting element, and the detection circuit detects a resistance value between the two points of the variable resistance element as an electric signal.
(20) The twentieth feature of the present invention resides in a force detector having the nineteenth feature:
wherein a variable resistance element has a first resistor and a second resistor disposed at a position opposed to the first resistor, and a surface of at least one resistor of the first and second resistors, which is opposed to the other resistor, has an uneven structure to elastically deform, and a contact surface area between the first resistor and the second resistor changes in accordance with a pressure applied in response to an applied external force which is a detecting subject so that a resistance value between a predetermined point connected to the first resistor and a predetermined point connected to the second resistor changes in accordance with changes in the contact surface area.
(21) The twenty-first feature of the present invention resides in a force detector having the twentieth feature:
wherein the first resistor and the second resistor are formed from a sensitive conductive ink.
(22) The twenty-second feature of the present invention resides in a force detector having the twentieth or the twenty-first feature:
wherein the detection circuit has a circuit for detecting a resistance value between the two points of the resistors by applying a voltage between the two points, and control is carried out so that the voltage is applied in the detection mode and is not applied in the standby mode.
(23) The twenty-third feature of the present invention resides in a force detector having the twenty-second feature:
wherein an electrical conductive/insulated condition between the pair of contacting electrodes comprising a switching element is used as an ON/OFF switch to apply a voltage to the two points of the resistors.
(24) The twenty-fourth feature of the present invention resides in a force detector having one of the first to the twenty-third features:
wherein an operation panel made of a rigid material is attached to the elastic deformable body, and the elastic deformable body deforms based on an operational input applied to the operation panel.
(25) The twenty-fifth feature of the present invention resides in a force detector having one of the first to the twenty-fourth features:
wherein the elastic deformable body comprises a film portion disposed almost in parallel to an upper surface of the substrate, a side wall portion for fixing a surrounding of the film portion to the upper surface of the substrate, and columnar projections extending downward from a plurality of positions of a lower surface of the film portion, at least a part of the film portion and the columnar projections being made of elastic material.
(26) The twenty-sixth feature of the present invention resides in a force detector having the twenty-fifth feature:
wherein the elastic deformable body is made of an integrally-molded rubber.
(27) The twenty-seventh feature of the present invention resides in an input device for an electronic apparatus for applying operational input indicating an operation amount in a predetermined direction to the electronic apparatus which executes particular processing based on a predetermined program, wherein the input device comprises a force detector having one of the first to the twenty-sixth features, and handles an external force detected by the force detector as an operation amount.